Pear trees add beauty to any landscape with their bright, white blooms and brilliant, orange leaves in the fall. In fact, pear trees are often planted as ornamental trees as well as for their sweet, juicy fruit. Unfortunately, pear trees are susceptible to a fungus called "pear trellis rust." While not as common in the United States as in Europe, it has been found in Washington state and California, as well as in British Columbia. Treat your pear tree for rust at the first signs of infection.
Examine the leaves of your pear tree carefully in early spring as they emerge. Look for tiny orange spots on the tops and undersides of the leaves. If left untreated, these spots will grow larger and turn black by June, and the tree will develop swollen orange or gray lumps (galls), which shelter spore growth.
Slip on some gardening gloves and pluck off as many of the infected leaves as you can reach. This will not harm the tree and will prevent the spread of the fungus. Simply drop them to the ground, as the fungus will die as soon as the leaves dry up.
Cut off heavily infected branches. Cut off the branch at an angle and as close to the main horizontal branch or trunk as possible. Also prune any galls (swollen tree tissue; often gray or orange) that may develop at the base of twigs.
Consider relocating any nearby juniper trees. This fungus also infects juniper trees and easily jumps from there to nearby pear trees. Leaving infected trees within close proximity to one another will only increase the severity of the disease each year.